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Unformatted text preview: Although many cannot be distinguished by appearance, this group has some highly unusual characteristics. The major difference first discovered is that their cell walls lack peptidoglycan. It has more recently been determined that all members of this group share many rRNA sequences which are different from those of all other living organisms. They are able to survive in extreme environmental conditions, use unusual sources of nutrition, and/or produce unusual end products of metabolism. Archaea: May be gram-positive or gram-negative May be cocci, rods, or spirals Include a few species of unusual morphology May be aerobic, facultatively anaerobic, or strictly anaerobic Nutritional requirements vary from chemoautotrophs to photoautotrophs to chemoheterotrophs...
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- Fall '09